The invention relates to a luminaire comprising a housing which accommodates a holder for an electric lamp. The housing has a base portion which is closed by a cover which is at least in part transparent, and a venting opening provided in the wall of the base portion.
Such a luminaire is known from German Gebrauchsmuster No. 1940617 and is frequently used to illuminate moist spaces. Due to the presence of venting openings, the temperature in the housing is prevented from increasing to an excessively high value during operation of a lamp arranged in the luminaire. In the housing of this luminaire, a comparatively large number of venting openings are provided through the base portion. These openings are in the form of slots formed in special spacer lugs, by means of which the housing can be secured to a ceiling. This construction, according to the Gebrauchsmuster, prevents water flowing into the housing, when the housing is secured to the ceiling. However, it has been found that, when such a luminaire is mounted on a wall in a position deviating from the horizontal, such as on a vertical wall, there is a risk nevertheless that water enters the housing and cannot escape.
This is especially disadvantageous in luminaires comprising a housing of comparatively small dimensions. It has been found that water and dust can then readily reach the current-conveying parts in the housing. Thus this known luminaire does not satisfy international standards with respect to water- and dusttightness (for example IP 54, as described in the document CIE 598-1 (1979)).